Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 231743
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
943 AM PST Thu Nov 23 2017

.SYNOPSIS...

Record or near record temperatures are forecast to continue
through Friday as the strong upper ridge and weak offshore flow
continues to persist over the region. An area of low pressure
will approach by Sunday with increasing clouds and cooler
temperatures. There is a chance of showers for areas north of
Point Conception Sunday night into Monday. Surface high pressure
will build into the Great Basin early next week allowing for
gusty offshore winds to develop by late Monday through early
Wednesday.

&&

.SHORT TERM...(TDY-SAT)

A strong upper-level ridge of high pressure remains over Southern
California today. The ridge, centered off the Baja California
Coast, and offshore flow will keep a very warm and dry air mass
in place across the area. Surface pressure gradients remain
moderately-to-strongly offshore this morning, although weaker
relative to yesterday. Record heat is forecast for some areas on
this Thanksgiving Day, especially for the valley areas.

The ridge axis will continue move east of the area throughout
today and tonight as the ridge starts to flatten. A broad trough
of low pressure over the Eastern Pacific Ocean, phasing with a
weaker trough near British Columbia, will dig into and displace
the ridge through the weekend.

No updates are planned at this time.

*** FROM PREVIOUS DISCUSSION ***

The highest temperature ever recorded on Thanksgiving (which is
not the same a daily record since it falls on different dates) in
Downtown Los Angeles was 90 degrees, set on November 26th, 1903.

Max temps however will still be well above each day...today temps
will be 18 to 22 degrees above normal...12 to 18 degrees above
normal on Friday and 8 to 12 degrees on Saturday.

.LONG TERM...(SUN-WED)

A stronger upper low moves into Pac NW on Sunday and pushes the
ridge away to the south and east. A weak cold front will approach
the area Sunday afternoon. Clouds will increase through the day
esp over SLO and SBA counties. A slight chc of rain will develop
over NW SLO county later in the afternoon. There will be an
increasing chc of rain Saturday night into early Sunday morning
across SLO and SBA counties as the front moves over the area. A
chc of rain will persist over the interior and north slopes during
the day Monday. Max temps will fall to normal across most of SLO
and SBA counties. Temps across VTA and LA counties will continue
to fall but will still be above normal.

Strong north to south gradients will develop once the trough axis
moves to the east of the region on Monday. The GFS and EC agree
that a strong north-northeast wind event is setting up for Monday
night and Tuesday. The GFS forecasts a 1040 mb surface high over
Idaho Tuesday morning, strengthening to a 1043 by Wednesday. The
GFS fcst LAX-DAG grad for Tuesday is -9 MB and 5.5 MB Wednesday
morning. There will be moderate north winds Monday night with the
strongest winds across the SBA south coast and the I-5 corridor.
The winds will turn to the NE Tuesday morning and a classic Santa
Ana will set up. It will be at least a moderate event and if the
upper level support lines up it could be a strong event. The Santa
Ana winds will continue into Wednesday but they will be weaker.

Monday will be the coolest day due to the clouds and lower hgts.
Max temps will rebound Tue and Wed but not as much as one might
think due to the large amount of cool air moving into the air from
the E. Min temps Tuesday and esp Wednesday will be below normal in
the non windy areas. Interior sections will likely see some frost
and perhaps even some freezing conds.

&&

.AVIATION...23/1630Z.

At 1600Z, there was a surface-based inversion at KLAX. The top of
the inversion was 1200 feet with a temperature of 28 degrees
Celsius.

High confidence in 18Z TAF package as weak offshore flow keeps all
sites VFR through the period.

KLAX...high confidence in 18Z TAF.

KBUR...high confidence in 18Z TAF.

&&

.MARINE...23/800 AM.

For the Outer Waters, moderate to high confidence in current
forecast. Small Craft Advisory (SCA) level winds will develop this
afternoon across PZZ670/673 and remain at SCA levels through
Friday afternoon. For PZZ676, SCA level wind gusts will be more
localized. Winds will diminish all areas on Saturday. However for
Sunday/Monday, west to northwest winds will increase with SCA
level winds likely.

For the Inner Waters, high confidence in current forecast. For the
waters north of Point Sal, winds and seas are expected to remain
below SCA levels through Sunday with a chance of SCA level winds
on Monday. For the waters south of Point Conception, winds and
seas will remain below SCA levels through Saturday. On Sunday,
northwest winds will begin to increase with a chance of SCA level
winds across western sections on Sunday and Monday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect from 3 PM this afternoon to 3
      PM PST Friday for zones 670-673. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK...(SAT-WED)

There is the potential for elevated to critical fire weather
conditions Monday through Wednesday for portions of Southwest
California. From Monday into Monday night, there is the potential
for strong northerly winds, followed by the potential for
strong Santa Ana winds and low humidities on Tuesday, with gusty
offshore winds lingering into Wednesday.

&&

$$

PUBLIC...Hall/Rorke
AVIATION...RAT
MARINE...RAT
SYNOPSIS...Kaplan

weather.gov/losangeles


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